1.substrvar str = "Hello world!";document.write(str.substr(3));输出：lo world!var str = "Hello world!";document.write(str.substr(3,7));输出：lo worl2.toFixed(四舍五入)var num = new Number(12.38)；document.write(num.toFixed(1));输出：12.4
3.floor(向下取整)Math.floor(0.60); ??结果：0Math.floor(0.40); ???????0Math.floor(5); ?????????5Math.floor(5.1); ???????5Math.floor(-5.1); ??????-6Math.floor(-5.9); ??????-63.ceil(向上取整)Math.ceil(0.60); ??结果：1Math.ceil(0.40); ???????1Math.ceil(5); ??????????5Math.ceil(5.1); ????????6Math.ceil(-5.1); ??????-5Math.ceil(-5.9); ??????-54.round(四舍五入)Math.round(0.60); ??结果：1Math.round(0.40); ???????0Math.round(5); ??????????5Math.round(5.1); ????????5Math.round(-5.1); ??????-5Math.round(-5.9); ??????-6使用floor配合*100/100来实现向下取整截取小数点后两位var num = 22.13758;console.log(Math.floor(num*100)/100);console.log(Math.ceil(num*100)/100);console.log(Math.round(num*100)/100);console.log(num.toFixed(2));输出：22.13 ????22.14 ????22.14 ????22.14
js截取小数点后面2位
原文地址：https://www.cnblogs.com/QW-lzm/p/9684084.html